In just the past two weeks, the rate on a 30-year, fixed-rate mortgage has risen to 5.6 percent from 4.9 percent, ending a boom in refinancing and working against a budding recovery in the housing market. Rates on corporate borrowing have also risen, making it more expensive for companies to expand. And the government has been forced to pay more to finance its deficit.

Since the beginning of the year, historically low mortgage rates have had a twin benefit for the economy: They have allowed homeowners to refinance about $1.5 trillion worth of mortgages, thus lowering monthly payments and leaving people with more money to spend on goods and services. Low rates have also created greater incentive for people to buy homes, despite continuing troubles in the housing market.

The abrupt rise in rates has removed that key stimulant for the economy.

The rise has many causes, some of which reflect good news. As investors have grown more confident about the future, for example, they have become more inclined to put money in risky investments, such as the stock market, rather than lending it to the U.S. government and to government-backed mortgage companies.

But other causes give more reason for worry. Investors around the world are increasingly fearful that Congress and the Obama administration will be unwilling to bring taxes and spending in line in the years ahead. That makes the U.S. government appear to be a riskier borrower, leading those who lend to it to demand higher interest payments.

The Federal Reserve now finds itself in a box. It could try to lower rates by buying government debt. It has already said it would buy $1.5 trillion in U.S. Treasuries and mortgage-related securities this year to try to stimulate growth.

But doing so would likely only deepen fears that the Fed will print money to fund government deficits in the future. That possibility -- while rejected by Fed officials and many mainstream economists -- means that expanding purchases might not have the intended effect of lowering rates. It could even drive them up further.

Rates remain very low by historical levels. But the yield on 10-year Treasury bonds has risen to almost 4 percent this week from 3.1 percent on March 14. (It edged down yesterday to 3.9 percent.)

A wide range of other rates are essentially moving in tandem with that rate, including mortgages. That shift has far-reaching implications.

"Households really have no capacity to afford higher rates at this point," said Scott Anderson, a senior economist at Wells Fargo. "It affects the cost of any long-term borrowing a consumer or business might do, whether it's auto loans, mortgages or business credit."

The number of refinance transactions has dropped 62 percent since early April, according to a survey by the Mortgage Bankers Association.